Conventionally, a weather strip having connections has been typically manufactured by cutting a rubber blend product of an ethylene/propylene/non-conjugated diene terpolymer (EDPM) that is formed by extrusion and vulcanization, placing the same in a mold from one or both sides of the mold, injecting a rubber molding material of a similar kind to the EPDM rubber blend into a cavity formed in the mold, and then performing vulcanization and molding.
Further, in place of the vulcanized rubber using a ethylene/propylene/non-conjugated diene terpolymer (EPDM), a thermoplastic elastomer (composition) that does not need to be vulcanized has come into use as the material for molding, from the viewpoint of productivity, environmental affinity and weight reduction.
In general, since a vulcanized rubber and a thermoplastic elastomer cannot be bonded to each other by vulcanization or the like, these components are integrated using an adhesive. However, this method is not considered to be sufficient from the viewpoint of productivity and environmental affinity. Further, sufficient adhesion is not achieved even when thermoplastic elastomer components are adhered to each other.
Addition of a resin containing a polar group is one technique directed to the composition of thermoplastic elastomer (Japanese Patent Application Laid-Open (JP-A) Nos. 2-115249, 8-244068, and 10-324200). However, when a resin containing a polar group is added, releasing properties of the molded product from a mold may deteriorate during molding, and thus extension of the molding cycle may occur. Further, a thermoplastic elastomer using an α-olefin non-crystalline polymer having a viscosity of not more than a specific degree has been proposed (Japanese Patent No. 3693017). In this case, however, a sufficient level of adhesion is not achieved and elasticity of the rubber may deteriorate.
Further, addition of a microcrystalline polypropylene to a conventional vulcanized rubber composition is one technique for producing the aforementioned vulcanized rubber (JP-A No. 10-7849). However, when a microcrystalline polypropylene such as atactic polypropylene is added, the elasticity of a conventional rubber may deteriorate, and the stickiness or hardness of the molded product may increase with time.
In addition to the techniques concerning the composition of thermoplastic elastomer and vulcanized rubber as mentioned above, there is a technique of achieving an anchoring effect by forming irregularities on a cut surface of the vulcanized rubber (JP-A No. 9-118133) and a technique of applying a polyolefin resin powder on a cut surface of the vulcanized rubber (JP-A No. 6-47816). However, these techniques are unsatisfactory insofar as improvements in adhesion are insufficient in view of the reduction in productivity caused by these techniques.
Accordingly, there is demand for a thermoplastic elastomer that forms a molded product that exhibits a sufficient level of adhesion with respect to a vulcanized rubber or a thermoplastic elastomer without the use of an adhesive layer, and a molded product formed by welding this elastomer to a vulcanized rubber or a thermoplastic elastomer. Further, there is demand for a thermoplastic elastomer that forms a light-weight molded product that exhibits sufficient hardness and rubber elasticity as a thermoplastic elastomer and exhibits excellent molding properties and economic efficiency, and a molded product formed by welding this elastomer to a vulcanized rubber or a thermoplastic elastomer.